We present molecular dynamics evidence for the nonanalytic effects of
the long-range dispersion forces on the capillary waves fluctuations of
a Lennard-Jones liquid surface. The results of the intrinsic sampling
method, for the analysis of the instantaneous interfacial shape, are
obtained in large systems for several cut-off distances of the potential
tail, and they show good agreement with the theoretical prediction by
Napiorkowski and Dietrich, based on a density functional analysis. The
enhancement of the capillary waves is quantified to be within 1% for a
simple liquid near its triple point.